1. Technical Field of the Invention
The present invention relates to rotational hinge mechanisms, for example, those used on the flip cover of a cellular telephone, and more particularly, to a method for damping a spring biased motion of a rotational hinge mechanism.
2. Description of Related Art
Rotational hinge mechanisms are utilized on devices that contain a so called "flip cover" that rotates between closed and opened positions on an attached body. One widespread use of a rotational hinge mechanism is within cellular telephone products wherein a flip cover is used to cover a keypad of the telephone when it is not in use. The flip cover may also include a microphone for receiving voice input from a user of the telephone when the flip cover is in the extended position. The rotational hinge mechanism for flip covers utilizes a spring-loaded action to move between the opened and closed positions. Existing rotational damping mechanisms utilize a disc shaped blade which rotates in shallow reservoir of viscous fluid. The mechanism is attached to the axis of the rotational hinge mechanism of the flip cover such that the disc shaped blade rotates about the axis of the rotational hinge.
This type of damping mechanism requires a relatively large diameter disc shaped blade in order to effectively damp the motion of the flip cover. In cellular telephone applications, where size is important, the thickness of the device must be minimized. Thus, a damping mechanism having a large diameter disc shaped blade works against the desire for smaller cellular telephone units. Thus, some manner for damping the motion of a rotational spring using a smaller mechanism is desired.